Module frames for the reception of plug-in electronic modules are known in the industrial electronic field. One version of such a module frame includes two side walls and four parallel module bars, which border with their two-sided front faces on the two side walls. A metal cover and a metal bottom as well as a rear panel can supplement the module frame to a chassis, from whose open front side the plug-in modules are slid into on inserted guides. The module bars can also be integrated parts of the metal cover, the metal bottom respectively; such a module frame with integrated module bars is, for example, described in the DE 198 17 089 C1.
The plug-in modules are inserted into the module frame on guides from the front in such a way, that the partial front panels of the plug-in modules are adjacent to each other. Each plug-in module is, with the help of multipolar plug connectors, connected on the rear panel of the module frame with a rear wiring board, the so-called back plane. Due to the ever-increasing packing density on the individual plug-in modules and the progressing miniaturization of electronic components, plug connectors with always increasing numbers of poles. The individual contacts are hereby arranged in several rows next to each other. Great forces, which increase proportionally to the number of the poles of the plug connector, are necessary for the insertion and extraction of the plug connectors from the contact strip. Without suitable help, devices such as the plug-in modules cannot be loosened from the module frames, nor is it possible to establish a reliable plug connection between the plug-in module and the back plane.
Lever systems with operation grips in different versions are known as plug-in and pull aides. The plug-in and pull aides are located in the upper and/or lower front area of the plug-in modules.
German Patent DE 44 28 529 C1 reveals a device for the extraction of plug-in modules from a module frame with a module bar. The plug-in module has an angle lever as well as a holding block for a front panel and a circuit board. The angle lever, which is rotatable around a swiveling axis in the holding block, includes a long lever arm that is formed as a grip and a short lever arm that has two push-off shoulders that have different distances to the swiveling axis. The module bar has a small strip attached to the front which extends the module bar forward so that an overhang, the so called roof, is created. During the extraction of the plug-in modules from the module frame the two push-off shoulders push off in succession from the attached strip.
The currently known plug-in and pull aides have several disadvantages.
The dimensions of the front overhang (roof) of the module bar are determined by the standard. The roof is formed as a narrow crosspiece with rectangle sharp edged recesses. The front contact surface is only a few millimeters high. The push-off shoulders of the lever can therefore only grip at a small contact surface, so that a very high contact pressure is generated during the transfer of the lever forces to the module bar.
The module bar and its overhanging roof are usually produced from metal. To avoid unwanted metal abrasion the angle levers and the push-off shoulders are often produced from plastic. When the push-off shoulders glide under high contact pressure over the sharp edges of the module bars, the additional problem is generated that the plastic adapts to the sharp metal edge due to flexible deformation. This kind of unwanted shaping additionally increases the existing frictional forces.
The lever forces appearing during the insertion and the extraction have a component in the direction of insertion or extraction and a component vertical to this direction. The vertical component of the lever force has an effect on the small edge of the roof of the module bar parallel to the front side of the module bar. If very high lever forces are transferred, the module bar bends, so that the lever slips off the module bar and finally does not engage any more. The slipping of the lever is further aided by the very small contact surface of the overhanging roof, which offers the lever only a small abutment.
For module bars without a roof overhanging to the front, the push-off shoulders can only grip directly on the front side of the module bar during the extraction of the plug-in module. But the front side of the module bar is interrupted by the common T-groove. The remaining contact surfaces on the front side, from which the push-off shoulders push off, are barely larger than the contact surfaces of the overhanging roof. Very high contact pressures are generated by the gripping lever as well.
A levering of the plug-in modules into the module frame is currently only possible at module bars with roof, since the push-off shoulders grip into the recesses of the roof strip of the module bar and push off from the inner surface of these recesses that are facing away from the module bar. Common module bars, meaning such without roof, have no abutment for the levering.